Compact serviceable diesel heater method and apparatus

ABSTRACT

A diesel heater has two compartments with the components which are frequently serviced being located in one of the compartments which is easily accessible to the user. The heater is of reduced size and weight for smaller coaches and boats and the control system allows for maximum safety and flexibility in operating from AC power, engine power or burner combustion.

INTRODUCTION

This application relates to a heater principally for use in recreational vehicle and marine applications and, more particularly to a diesel heater made for use in smaller recreational vehicles and smaller boats.

BACKGROUND OF THE INVENTION

Diesel heaters are of course well known. In larger recreational vehicles and larger boats, diesel fuel is used for engine fuel and the use of such diesel for auxiliary heating units is convenient and far safer than the use of propane and other gaseous fuels. The use of such diesel heaters in larger recreational vehicles and larger boats is generally associated with hydronic heating; that is, the diesel heater heats a coolant which coolant circulates through the recreational vehicle or coach and also through the boat in marine applications. Hydronic heating is highly desirable but it is expensive which makes it's application limited to more expensive coaches and boats.

In addition to the circulation of coolant for heat in hydronic heating, the circulation of coolant is also used to obtain potable hot water for showers, sinks and faucets and the like. In this latter application, the coolant is generally circulated through a heat exchanger which transfers the coolant heat to the potable water which, in turn, is circulated to the various points of use in the coach or boat.

Typically, the heaters used to heat the coolant and to circulate the coolant are large heaters. In larger coaches and boats, it is not a problem to find an area large enough within which such a heater can be positioned. Such heaters may be located in areas outside the living quarters with panels that open and close allowing access to the heaters. To reduce the installation footprint, the OASIS (Trademark) diesel heater manufactured by International

Thermal Research Ltd. of Vancouver, Canada has an associated distribution module. The use of the distribution module reduces the footprint of the area needed for heater installation. The module contains the necessary pumps and heat exchangers and may be located wherever space is available thereby allowing increased installation flexibility.

In smaller coaches, typically known as Class B motorhomes, there is far less space available for the installation of large diesel heaters. Space is a precious commodity and expense is a significant criterion for heater selection. As a result, propane has typically been widely used for heater fuel, hot water heat and heat within the living quarters. The use of propane is relatively inexpensive and propane heaters do not take up significant space. Propane, however, is not a benign fuel and many accidents have happened because care was not appropriately taken in the use of such fuel.

SUMMARY OF THE INVENTION

According to one aspect of the invention, there is provided a diesel heater having a coolant tank, a diesel fuelled burner having a nozzle to provide combustion within said heater, a combustion chamber positioned within said coolant tank, said nozzle extending into said combustion chamber, a combustion fan to provide air to said diesel fuelled burner, a compressor to provide air under pressure to said nozzle, a heat exchanger to allow circulation of said coolant and potable water, said heat exchanger exchanging heat between said coolant and said potable water and a mixing valve to control the heat of said heated potable water which leaves said mixing valve, said heat exchanger, said mixing valve, said compressor and said combustion fan being substantially enclosed within a compartment of said diesel fuelled heater.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Specific embodiments of the invention will now be described, by way of example only, with the use of drawings in which:

FIG. 1 is a isometric view of the diesel heater according to the invention, particularly illustrating the compartment positioned besides the coolant tank and burner;

FIG. 2 is a side view of the heater of FIG. 1 particularly illustrating the side compartment but without it's cover and illustrating the various operating components of the heater positioned within the compartment;

FIG. 3 is a front view of the diesel heater of FIG. 1 diagrammatically illustrating the tank and burner compartment as well as the side compartment connected thereto;

FIG. 4 is a plan view of the diesel heater of FIG. 1 particularly illustrating the fresh air inlet, the mixing valve adjustment knob, the water, coolant and fuel inlets and outlets and the coolant flow tube to the heat exchanger;

FIG. 5 is a plan view similar to FIG. 4 but with the casing which encloses the coolant tank being removed in order to view the electrical components operable on and from the coolant tank; and

FIG. 6 is a diagrammatic isometric view of the coolant tank removed from the diesel heater and particularly illustrating the burner and combustion cavity in the coolant tank, the position of the electrical element and aquastats relative to the coolant tank, the hot coolant fitting and the exhaust connection which allows exit of the combustion gases from the combustion chamber.

DESCRIPTION OF SPECIFIC EMBODIMENT

Referring now to the drawings, the diesel heater according to the invention is generally illustrated at 100 in FIG. 1. The heater includes a casing generally illustrated at 101. The casing 101 includes two sections, namely component section 102 and burner box section 103. A wiring harness 104 extends from a remotely located control board (not illustrated) to the various operating components within the component section 102 as will be explained.

The combustion fan 110 (FIG. 2) draws air from the ambient surroundings through air inlet 111 (FIG. 1) which extends through the top of component section 102. Likewise, several fittings are provided and extend through the top of the component section 102. Potable water in fitting 112 and potable water out fitting 113 are provided as well as coolant in fitting 120 and coolant out fitting 121. The adjustment head 114 of the mixing valve 122 (FIG. 2) also extends outwardly from the top of component casing 102 to allow external adjustment of the mixing valve 122 without removal of the component casing 102.

Three closure panels 123, 124, 130 are used to cover the DC aquastats generally shown at 131 (FIG. 5), the AC aquastats generally shown at 132 and the AC electrical connection 133, respectively. Two fittings, the first for fuel in 140 and the second for fuel out 141 also extend outwardly from the top of component casing 102.

A coolant temperature gauge 142 is positioned on the front panel 143 of the component section 102 and shows the temperature of the coolant in the tank 150 (FIG. 5). An hour meter 151 is similarly positioned on the front panel 143 and shows operating hours of the heater 100. A fresh water drain 152 allows the potable water to be drained from the heater 100 in order to winterize the heater 100 or to change the potable water within the heater 100 if desired.

A sight glass 153 in the front panel of the coolant tank section 103 allows a user or service person to view the flame produced within the coolant chamber from a position in front of the heater 100 when the heater 100 is under operation.

Reference is now made to FIG. 2 which illustrates the component section 102 of the heater 100 with the closing panel 154 (FIG. 1) opened. There are several opening components positioned with the component section 102 which components are exposed with the removal of the panel 154 and thus are readily available for service or replacement when desired.

A heat exchanger 160 is bolted to the end panel 161 of the component section 102 by nuts 162. Engine preheat couplings 163, 164 also extend through the end panel 161. The engine preheat couplings 163, 164 are used in the event it is intended to use the heater 100 to preheat the engine block (not shown) of the vehicle in which the heater 100 is installed.

The combustion fan 110 in attached to the air inlet 111. The combustion fan provides air to support combustion of the diesel fuel withing the burner tube 170 (FIG. 3). A fuel pump 171 and a fuel regulator 172 provide and control fuel for the nozzle 173 (FIG. 3) as will be explained. A compressor 174 located in the component section provides air under pressure to the nozzle 173. A mixing valve 122 is located in the component section 102 and the mixing valve control knob 114 is rotated so as to increase or decrease the temperature of the potable water circulating through the system. The cold potable water enters the heater 100 through fitting 214 and divides with one stream going to the heat exchanger 160 where a cold water aquastat 214 monitors the temperate of the incoming cold water and initiates a call for heat when the cool water flows and the second stream entering the mixing valve 122. A heat exchanger aquastat 180 is positioned on the heat exchanger 160 to measure the temperature of the potable water within the heat exchanger 160 and to shut down the heater 100 in the event the temperature sensed by the aquastat 180 exceeds a predetermined value.

Referring now to FIG. 3, the coolant tank section 103 is shown diagrammatically as if the coolant tank panel 181 was not in place. The coolant tank 182 (FIG. 6) is positioned within the coolant tank section 103. The nozzle 173 emits atomised air and fuel which is ignited by an ignitor 183 which is generally held in position within an ignitor holder tube 184. A flame sensor 190 senses the presence or absence of a flame in the burner tube 170 and shuts down the heater 100 if no flame is sensed when it should be incandescent.

An electric element 191 is mounted within the coolant tank 182. The electric element 191 allows the coolant with the coolant tank 182 to be heated when combustion is not taking place such as when the boat or coach is not under operation and an electrical power supply or shore power is available. An electrical element wattage of approximately 1500 watts is conveniently used.

A fuel solenoid 192 is connected to the fuel block 220. When the fuel solenoid 192 is open, fuel passes to the nozzle 173. When the fuel solenoid 192 is closed, fuel is prevented from flowing to the nozzle 173.

The temperature sending unit 193 (see also FIG. 6) is mounted within the coolant in coolant tank 182 adjacent the exhaust box where the temperature of the coolant is the highest. This temperature is displayed on the temperature gauge 142.

Reference is now made to FIG. 4 where the hot coolant line 194 runs from the coolant tank 182 to the heat exchanger 160. The coolant in fitting 121 provides coolant to the coolant tank 182 and the coolant out fitting 120 allows coolant to flow outwardly from the coolant tank 182 as it circulates through the coolant tank 182.

Reference is now made to FIG. 5 where a plan view of the heater 100 with the top coolant tank section panel 200 (FIG. 1) is removed so as to expose the tank 150. There are three (3) DC aquastats generally illustrated at 201 (see also FIG. 6). The three (3) aquastats include a cycling aquastat 204 conveniently used to keep the coolant temperature below 180 deg.F., a high limit aquastat 202 which provides an indication to the controller (not illustrated) that the coolant temperature has exceeded 205 deg.F. and an overheat aquastat 203 which cuts power to the fuel solenoid 192 when the temperature of the coolant exceeds 190 deg.F.

There are two AC aquastats generally illustrated at 210 which include a cycling AC aquastat 211 and an AC backup aquastat 212. The burner box 213 holds the components which are described in relation to FIG. 3 above, namely the fuel solenoid 192, the igniter 183, the igniter holder tube 184, the flame sensor 190, the fuel block 215 which holds the nozzle 173.

The exhaust fitting 213 (FIG. 6) extends downwardly from the exhaust box (not shown). The exhaust box has the ability to easily use an up or down exhaust fitting. The coolant tank used in the diesel heater according to the present invention is similar to the coolant tank which is the subject of our application Ser. No. 10/848,780 filed May 18, 2004 and now issued as U.S. Pat. No. 8,118,239 dated Feb. 21, 2012, the contents of which are incorporated herein by reference. Thus, the diesel heater 100 can readily be constructed for either coach use where a down exhaust configuration is generally used or an up exhaust configuration which is generally used in boats.

With the exhaust box moved from the top of the coolant tank to the side of the tank as disclosed in the '239 patent, there is a delay in the hot coolant surrounding the exhaust box reaching the position of the cycling aquastat at the top of the tank. This results in a delay in the cycling aquastat shutting off the burner. This results in a higher temperature at the location of the “overheat” aquastat. In this case, when the cycling aquastat shuts OFF the burner, the temperature at the “overheat” aquastat position continues to rise until the “overheat” aquastat triggers the alarm a minute or two after the burner has cycled off. Since this is a nuisance alarm only, the temperature of the cycling aquastat is lowered to account for the temperature spike. Alternatively the location of the cycling aquastat could be moved which could result in lower coolant temperature. Accordingly, a further aquastat is positioned in the system that acts as a backup to the “overheat” aquastat. This aquastat is manually resettable and is wired in series with the fuel solenoid. If this aquastat triggers, the fuel solenoid will shut off, and the flame will extinguish. To overcome the temperature spike, the wiring for the “overheat” and “high limit” aquastats was reversed. With this wiring, the temperature spike will still trigger the “overheat” aquastat which will cut power to the fuel solenoid, but since the heater has already shut off (due to the cycling aquastat), this has no effect. If the cycling aquastat fails, the “overheat” aquastat cuts power to the fuel solenoid and extinguishes the burner flame. Thus, the wiring configuration eliminates the noise from the alarm but continues to maintain safety.

If the “high limit” aquastat is triggered, it indicates that the “cycling” and the “overheat” aquastats have failed. If this happens, the aquastat will indicate to the control board that the temperature has gone too high and the control board will shut the heater off and sound the alarm. The user will then need to manually re-set the aquastat. The “high limit” aquastat is intended be the only manually resettable aquastat in the system. Thus, maximum coolant temperature is maintained without a nuisance alarm.

Operation

In operation, it will be assumed that the diesel heater 100 is completely installed in a coach (not illustrated) where a down exhaust configuration using a down exhaust fitting 213 as viewed in FIG. 6 is used. It will further be assumed that the coach fuel tank is installed with the fuel being pumped by way of fuel pump 171 (FIG. 2) to fuel regulator 172 and thence to solenoid 192 before passing to the nozzle 173 of the fuel system. The compressor siphons fuel from the fuel regulator, through the fuel solenoid and to the nozzle, by way of the venturi create3d at the nozzle. The fuel pump 171 pumps fuel only to the fuel regulator 172.

A thermostat [not illustrated] is placed in the living area to monitor the temperature within the living area. Likewise, an aquastat positioned on the heat exchanger monitors the heat of the domestic water passing through the heat exchanger. Yet a further aquastat is positioned on the coolant tank to monitor the temperature of the coolant within the coolant tank and if the temperature reaches a predetermined temperature of greater than 180 deg.F., it will terminate combustion. If the aquastat located on the heat exchanger drops below a predetermined temperature, conveniently approximately 104 deg.F., a call for combustion will be initiated and the call for combustion will terminate when the domestic water aquastat reaches a temperature of approximately 140 deg.F.

There will be no combustion activity unless the heater receives a call for either hotter domestic water within the heat exchanger or if the heater receives a call for heat within the living area from the thermostat located there. The coolant temperature should conveniently be below 180 deg.F. or the burner will cycle off.

Following a call for heat, the igniter turns on as well as the coolant pump and coolant is them pumped through the heat exchanger. Following a ten (10) second period for the igniter to hat up, the compressor, the fuel pump, the fuel solenoid and the combustion fan simultaneously turn on. Combustion will then be taking place within the burner tube. After a thirty (30) second period so that the igniter can ignite the flame in the event of air bubbles in the fuel system which may extinguish the flame, the igniter turns off. Combustion will then be taking place within the burner tube. The combustion will continue until the coolant within the coolant tank reaches a temperature of approximately 180 deg.F. at which time the combustion will terminate. Likewise, if the water temperature of the water within the heat exchanger is greater than 140 deg.F., the aquastat located there will indicate to the control system that the call for domestic hot water has been satisfied and the control system will terminate combustion. It is noted that in the event the thermostat is calling for heat, the burner will not shut down although the demand for potable hot water has been satisfied and vice versa.

Following termination of combustion, the combustion fan continues to run as well as the coolant circulation pump for a period of two minutes. Following the shut down of the combustion process and the expiration of two (2) minutes, the heater waits for another call for heat before combustion will recommence.

An electric element is also positioned within the coolant tank which uses AC “shore” power to initiate the heating operation. There is a manually operated switch to initiate the element heating operation. A separate AC aquastat mounted on the coolant tank will also terminate element operation if the coolant tank temperature reaches 180 deg.F. A high limit aquastat will terminate operation if the coolant goes over 190 deg.F.

A further option available to the user is the ability to utilise the heater coolant for an engine “preheat” operation. In this event, a separate switch is installed that powers a pre-heat pump plumbed into the engine coolant loop. To pre-heat the engine, the switch for the pre-heat pump is turned on and the burner switch is also turned on. The thermostat is turned on to initiate a call for heat so the burner will fire.

The heater will then heat the coolant in the heating loop and circulate it through the heat exchanger. The engine pre-heat pump will circulate the engine coolant through the same heat exchanger, which will result in the heat transferring from the heating loop to the engine loop.

When the engine of the vehicle is in operation, the engine coolant is circulated through the heat exchanger. The engine aquastat mounted on the heat exchanger is used to indicate to the control board that heat from the engine is available. When the control board gets the indication, it will run the circulation pump if a thermostat or domestic water aquastat calls for heat. This allows the engine heat to be distributed throughout the system. Thus, the burner switch can be left off and fuel used for the heater can be conserved.

Many modifications will readily occur to those skilled in the art to which the invention relates and the specific embodiments described may be taken by way of example only and not as limiting the invention as defined in accordance with the accompanying claims. 

I claim:
 1. A diesel heater having a coolant tank, a diesel fuelled burner having a nozzle to provide combustion within said heater, a combustion chamber positioned within said coolant tank, said nozzle extending into said combustion chamber, a combustion fan to provide air to said diesel fuelled burner, a compressor to provide air under pressure to said nozzle, a heat exchanger to allow circulation of said coolant and potable water, said heat exchanger exchanging heat between said coolant and said potable water and a mixing valve to control the heat of said heated potable water which leaves said mixing valve, said heat exchanger, said mixing valve, said compressor and said combustion fan being substantially enclosed within a compartment of said diesel fuelled heater. 